In this work we will study the interactions of two glycolytic enzymes, glyceraldehyde 3-phosphate dehydrogenase (GPDH) and phosphoglycerate kinase (PGK) with cell membranes. The binding of GPDH with human erythrocyte membranes has already been well characterized in previous studies under this project. Three specific studies will be carried out. 1. Binding of GPDH and PGK to Membranes in Cells other than Erythrocytes. In this investigation we plan to measure the amount of these enzymes bound to several mammalian cell membranes. The stoichiometry and affinity of the binding will be determined. The effects of ionic strength, pH and specific ligands on the binding of the enzymes will be measured and compared with the corresponding experiments already carried out with erythrocyte membranes. The protein of the membranes will be separated by SDS polyacrylamide gel electrophoresis and compared with erythrocyte membranes in order to see if there are common factors in the enzyme-membrane interactions in different tissues. 2. Binding of GPDH to Membranes during Maturation of the Erythrocyte. During maturation of erythrocytes the intracellular content of GPDH changes and the transport properties of the membrane alter. We plan to determine whether the binding of GPDH to the membrane is altered during maturation and, if so, to determine what factors may be important in this process. 3. PGK Binding to Erythrocyte Membranes. There is ample evidence suggesting that PGK is present in erythrocyte membranes formed by single step hemolysis (pink ghosts). The purified white ghosts which we have used to characterize GPDH binding have very little bound PGK activity. We propose to characterize the pink ghosts in order to find out what factors are different from the white ghost preparations and to establish how PGK binds to erythrocyte membranes.